Most computers can support various components and devices that comprise or interface with the computer in a variety of different ways. These components and devices must be supported by different software programs and operating environments running in the computer.
For example, a personal computer may connect to peripheral devices through one or more peripheral buses or ports. Examples of popular peripheral buses include a universal serial bus ("USB") or an IEEE 1394 serial bus ("1394 bus"). The USB is a two-wire serial personal computer bus, designed by a consortium of computer makers and suppliers, which can support many peripheral devices either in parallel or in a daisy chain configuration. The 1394 bus is also a two-wire serial personal computer bus, very similar to the USB. Specifications for the 1394 bus are available from the Institute of Electrical and Electronics Engineers, Inc. ("IEEE"), 345 East 47th Street, New York, N.Y. 10017-2394. For both the USB and the 1394 bus, when a device is connected to the bus, it provides a predetermined code that identifies its type and bandwidth requirements.
Problems occur when a computer implements an operating environment that is not aware of a specific type (e.g., does not provide appropriate device drivers) of device. To resolve these problems, the computer must implement device support outside of the operating environment. For example, if a computer uses a USB port for a USB keyboard while implementing a PS/2 operating environment (a PS/2 operating environment expects a PS/2 type keyboard), the computer's basic input/output system ("BIOS") can intercept data and software access to and from specific ports associated with the keyboard. The BIOS thereby "translates" the commands between the newer USB keyboard and the operating environment for use with older (or "legacy") keyboards by examining the internal processor ports and registers and "routing" data accordingly.
Continuing with the present example, if the processor writes a data value to port 60h (60 hexadecimal, which is a port defined for use by a PS/2 keyboard), the write instruction causes a system management interrupt ("SMI") trap. In response to the SMI trap, the BIOS instructs the processor to enter a system management mode. The BIOS then places the appropriate data in the processor's registers.
Similarly, the BIOS can be interrupted in order to be requested to go into standby mode. In order to determine what the BIOS was interrupted for, the BIOS must inspect the software instructions. The BIOS relies on data stored in the processor registers to determine this. The BIOS should then retrieve the appropriate data out of the processor's registers to make a decision or perform an action.
However, the BIOS may be interrupted for several reasons and may not be able to determine the reason from the hardware or the interrupt alone. A problem exists when the computer has multiple processors. In these computers, the BIOS has no way to know which of the processors in the multiprocessor system initiated the request. In the above-described examples, the BIOS must determine which of the processors instruction execution caused the interrupt to properly route the data to or from the USB keyboard.
Therefore, what is needed is a system and method for handling system management interrupts in a multiprocessor computer.